Social insects constitute a small but regular and deliberate part of the diet of sympatric western lowland gorillas and chimpanzees. I provide the first comparative and multidisciplinary study on this neglected aspect of their ecology. I examine whether they show niche differentiation in their insect diet, as they do in their plant diet, taking into account nutritional and ecological characteristics of their insect prey. In the first section of my study inter-site comparisons show that local traditions in insectivorous behaviour seem to exist in both chimpanzees and gorillas. However, at most great ape study sites detailed ecological data are lacking. Both study species also seem more insectivorous in secondary than in primary forest sites, which might partly be explained by a higher availability of prey species in secondary forest. Differences in prey choice between chimpanzees and gorillas in southeast Cameroon cannot only be explained by the capability of using tools, but also seem to be influenced by nutritional factors. Further, future research should focus on medicinal properties of ant and termite prey. In the second part it becomes clear that the study site in southeast Cameroon is a biodiversity hotspot of termites and ants. A wide variety and high density of microhabitats, as available at this site, is essential for high termite species diversity, which maintains optimal ecosystem functioning. I also found that ant assemblages in African rainforests are extremely dynamic and depend on a complex combination of availability of food resources, nest sites and predators. Chimpanzees and gorillas do not consume the most abundant termite and ant species. They choose species with very visible nesting sites or activity, although this is not necessarily the case with all their ant prey species. Finally, in the third section, my study demonstrates niche differentiation in the insect diet of chimpanzees and gorillas in southeast Cameroon. Chimpanzees use a ‘high-energy’ strategy and gorillas a ‘low-energy’ strategy when feeding on non-winged termites. Although ant grub consumption is underestimated, both seem to use a ‘low-energy’ strategy when feeding on ants.  These results are useful in conservation planning, zoo nutrition programs, paleo-ecological and cultural primatology studies.